1. Field of the Invention
The present invention relates to a levitator which may be mounted on a space station, for example, for use in material science experiments in space.
2. Description of the Related Art
FIG. 1 shows the arrangement of a prior art disclosed in W. K. Rhim, M. Collender, M. T. Hyson, W. T. Simms, and D. D. Elleman, "Development of an electrostatic positioner for space material processing", Rev. Sci. Instrum., 56, February 1985, pp. 307-317). In the figure, the reference numeral 1 denotes a charged sample, 2 a position detector for detecting the position of the sample 1, and 3 a variable power supply whose output voltage varies in accordance with the signal output from the position detector 2. The reference numerals 4a and 4b denote a pair of planar electrodes which are connected to two ends, respectively, of the variable power supply 3 and disposed in opposing relation to each other, 5a5b DC power supplies, and 6a, 6b ring electrodes each of which is disposed so as to surround a corresponding planar electrode 4a or 4b and to which a higher voltage is applied than that applied to the corresponding planar electrode from the DC power supply 5a (5b).
In operation, the position of the positively charged sample 1 is constantly monitored by the position detector 2 and the output of the variable power supply 3 is controlled so that the sample 1 is kept equidistant between the upper and lower electrodes in the vertical direction as viewed in the figure. Since higher voltages than those applied to the planar electrodes 4a and 4b are applied to the ring electrodes 6a and 6b, the sample 1 is also held stationary in the horizontal direction as viewed in FIG. 1.
Thus, an experiment, for instance, in which the sample 1 held in this way is heated by irradiation with light or the like can, for example, be carried out at a space station.
The conventional levitator arranged as described above suffers, however, from the following problems. Since the prior art merely controls the position of the sample through the planar and ring electrodes, it is incapable of rotating the sample in a controlled manner to heat it uniformly. In addition, the prior art is incapable of preventing a microgravity condition, which is a significant feature of material science experiments in space, from being destroyed by the spontaneous rotation of the sample itself due to convection, for instance.